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            <div><h4 class="title">
                <a name="asio.overview.posix.fork"></a><a class="link" href="fork.html" title="Fork">Fork</a>
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    <p>
        Asio supports programs that utilise the <code class="computeroutput"><span class="identifier">fork</span><span
            class="special">()</span></code> system call. Provided the program calls
        <code class="computeroutput"><span class="identifier">io_context</span><span class="special">.</span><span
                class="identifier">notify_fork</span><span class="special">()</span></code>
        at the appropriate times, Asio will recreate any internal file descriptors
        (such as the "self-pipe trick" descriptor used for waking up
        a reactor). The notification is usually performed as follows:
    </p>
    <pre class="programlisting"><span class="identifier">io_context_</span><span class="special">.</span><span
            class="identifier">notify_fork</span><span class="special">(</span><span class="identifier">asio</span><span
            class="special">::</span><span class="identifier">io_context</span><span class="special">::</span><span
            class="identifier">fork_prepare</span><span class="special">);</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">fork</span><span class="special">()</span> <span
                class="special">==</span> <span class="number">0</span><span class="special">)</span>
<span class="special">{</span>
  <span class="identifier">io_context_</span><span class="special">.</span><span
                class="identifier">notify_fork</span><span class="special">(</span><span
                class="identifier">asio</span><span class="special">::</span><span
                class="identifier">io_context</span><span class="special">::</span><span
                class="identifier">fork_child</span><span class="special">);</span>
  <span class="special">...</span>
<span class="special">}</span>
<span class="keyword">else</span>
<span class="special">{</span>
  <span class="identifier">io_context_</span><span class="special">.</span><span
                class="identifier">notify_fork</span><span class="special">(</span><span
                class="identifier">asio</span><span class="special">::</span><span
                class="identifier">io_context</span><span class="special">::</span><span
                class="identifier">fork_parent</span><span class="special">);</span>
  <span class="special">...</span>
<span class="special">}</span>
</pre>
    <p>
        User-defined services can also be made fork-aware by overriding the <code class="computeroutput"><span
            class="identifier">io_context</span><span class="special">::</span><span
            class="identifier">service</span><span class="special">::</span><span
            class="identifier">notify_fork</span><span class="special">()</span></code>
        virtual function.
    </p>
    <p>
        Note that any file descriptors accessible via Asio's public API (e.g. the
        descriptors underlying <code class="computeroutput"><span class="identifier">basic_socket</span><span
            class="special">&lt;&gt;</span></code>, <code class="computeroutput"><span
            class="identifier">posix</span><span class="special">::</span><span
            class="identifier">stream_descriptor</span></code>,
        etc.) are not altered during a fork. It is the program's responsibility
        to manage these as required.
    </p>
    <h6>
        <a name="asio.overview.posix.fork.h0"></a>
        <span><a name="asio.overview.posix.fork.see_also"></a></span><a class="link"
                                                                        href="fork.html#asio.overview.posix.fork.see_also">See
        Also</a>
    </h6>
    <p>
        <a class="link" href="../../reference/io_context/notify_fork.html" title="io_context::notify_fork">io_context::notify_fork()</a>,
        <a class="link" href="../../reference/io_context/fork_event.html" title="io_context::fork_event">io_context::fork_event</a>,
        <a class="link" href="../../reference/execution_context__service/notify_fork.html"
           title="execution_context::service::notify_fork">io_context::service::notify_fork()</a>,
        <a class="link" href="../../examples/cpp03_examples.html#asio.examples.cpp03_examples.fork">Fork examples</a>.
    </p>
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